IMPORTANT QUESTIONS ( CLASS 10) SCIENCE

                                                                CLASS 10

                                                   IMPORTANT QUESTIONS

                                                             CHEMISTRY 

                                                              CHAPTER 1

Q1
(a) State the law that is followed by balancing a chemical equation.
(b) Balance the following chemical equation: Na + H3O → NaOH + H2 (Board Term I, 2013)

Q2 Explain the significance of photosynthesis.

Write the balanced chemical equation involved in the process. (Board Term I, 2017)

Q3 Write balanced chemical equations for the following chemical reactions:
(a) Hydrogen + Chlorine → Hydrogen chloride
(b) Lead + Copper chloride → Lead chloride + Copper
(c) Zinc oxide + Carbon → Zinc + Carbon monoxide (Board Term I, 2014)

Q4 Calcium oxide reacts vigorously with water to produce slaked lime.
CaO(s) + H2O(l) → Ca(OH)2(aq)
This reaction can be classified as
(A) Combination reaction
(B) Exothermic reaction
(C) Endothermic reaction
(D) Oxidation reaction

Which of the following is a correct option? (2020)
(a) (A) and (C)
(b) (C) and (D)
(c) (A), (C) and (D)
(d) (A) and (B)

Q5 When hydrogen sulphide gas is passed through a blue solution of copper sulphate, a black precipitate of copper sulphide is obtained and the sulphuric acid so formed remains in the solution. The reaction is an example of a (2020)

(a) combination reaction
(b) displacement reaction
(c) decomposition reaction
(d) double displacement reaction.

Q6.
In a double displacement reaction such as the reaction between sodium sulphate solution and barium chloride solution :
(A) exchange of atoms takes place
(B) exchange of ions takes place
(C) a precipitate is produced
(D) an insoluble salt is produced
The correct option is (2020)
(a) (B) and (D)
(b) (A) and (C)
(c) only (B)
(d) (B), (C) and (D)

Q7Question 9.

In which of the following, the identity of initial substance remains unchanged? (2020)
(a) Curdling of milk
(b) Formation of crystals by process of crystallization
(c) Fermentation of grapes

(d) Digestion of food

Q8  Study the following equation of a chemical reaction: (Board Term 1, 2015)
H2 + Cl2 → 2HCl
(i) Identify the type of reaction.
(ii) Write a balanced chemical equation of another example of this type of reaction.

Q9 1 g of copper powder was taken in a China dish and heated. What change takes place on heating? When hydrogen gas is passed over this heated substance, a visible change is seen in it. Give the chemical equations of reactions, the name and the color of the products formed in each case. (2020)

Q10 A compound ‘A’ is used in the manufacture of cement. When dissolved in water, it evolves a large amount of heat and forms compound ‘B’.
(i) Identify A and B.
(ii) Write chemical equation for the reaction of A with water.
(iii) List two types of reaction in which this reaction may be classified. (2020)

Q11 Mention with reason the color changes observe when:
(i) silver chloride is exposed to sunlight.
(ii) copper powder is strongly heated in the presence of oxygen.
(iii) a piece of zinc is dropped in copper sulphate solution. (2020)

Q12 Lead nitrate solution is added to a test tube containing potassium iodide solution.
(a) Write the name and color of the compound precipitated.
(b) Write the balanced chemical equation for the reaction involved.
(c) Name the type of this reaction justifying your answer. (2020)

Q13 2 g of silver chloride is taken in a China dish and the China dish is placed in sunlight for sometime. What will be your observation in this case? Write the chemical reaction involved in the form of a balanced chemical equation. Identify the type of chemical reaction. (Delhi 2019)

Q14 Identify the type of reactions taking place in each of the following cases and write the balanced chemical equation for the reactions.
(a) Zinc reacts with silver nitrate to produce zinc nitrate and silver.
(b) Potassium iodide reacts with lead nitrate to produce potassium nitrate and lead iodide. (Delhi 2019)

Q15 You might have noted that when copper powder is heated in a China dish, the reddish brown surface of copper powder becomes coated with a black substance. (AI 2019)
(a) Why has this black substance formed?
(b) What is the black substance?
(c) Write the chemical equation of the reaction that takes place.
(d) How can the black coating on the surface be turned reddish brown?

Q16 Decomposition reactions require energy either in the form of heat or light or electricity for breaking down the reactants. Write one equation each for decomposition reactions where energy is supplied in the form of heat, light and electricity. (2018)

Q17 Take 3 g of barium hydroxide in a test tube, now add about 2 g of ammonium chloride and mix the contents with the help of a glass rod. Now touch the test tube from outside.
(i) What do you feel on touching the test tube?
(ii) State the inference about the type of reaction occurred.
(iii) Write the balanced chemical equation of the reaction involved. (Board Term I, 2017)

Q18 (a) A solution of potassium chloride when mixed with silver nitrate solution, an insoluble white substance is formed. Write the chemical reaction involved and also mention the type of the chemical reaction.
(b) Ferrous sulphate when heated, decomposes with the evolution of a gas having a characteristic odor of burning Sulphur. Write the chemical reaction involved and identify the type of reaction. (Board Term I, 2016)

Q19 What is a reduction reaction?
Identify the substances that are oxidised and the substances that are reduced in the following reactions. (Board Term I, 2015)
(a) Fe2O3 + 2Al → Al2O3 + 2Fe
(b) 2PbO + C → 2Pb + CO2

Q20 a) Can a displacement reaction be a redox reaction? Explain with the help of an example.
(b) Write the type of chemical reaction in the following:
(i) Reaction between an acid and a base
(ii) Rusting of iron. (Board Term I, 2017)

Q21 Mention the type of chemical reaction that takes place when: (Board Term I, 2013)
(i) a magnesium ribbon is burnt in air.
(ii) limestone is heated.
(iii) silver bromide is exposed to sunlight.
(iv) electricity is passed through acidified water.
(v) ammonia and hydrogen chloride are mixed with each other.
Write the chemical equation for each reaction.

Q22 What happens when food materials containing fats and oils are left for a long time? List two observable changes and suggest three ways by which this phenomenon can be prevented. (2020)

Q23 (i) Why is respiration considered as an exothermic reaction?
(ii) Write chemical name and the formula of the brown gas produced during thermal decomposition of lead nitrate.
(iii) Why do chips manufactures flush bags of chips with gas such as nitrogen? (Board Term I, 2015)

Q24 Write the chemical equation of the reaction in which the following changes have taken place with an example of each:
(i) Change in color
(ii) Change in temperature
(iii) Formation of precipitate

Q25 2g of ferrous sulphate crystals are heated in a dry boiling tube.
(i) List any two observations.
(ii) Name the type of chemical reaction taking place.
(iii) ‘Write the chemical equation for the reaction.

Q26  (a) Define a balanced chemical equation. Why should an equation be balanced?
(b) Write the balanced chemical equation for the following reaction:
(i) Phosphorus burns in presence of chlorine to form phosphorus penta chloride.
(ii) Burning of natural gas.
(iii) The process of respiration.

Q27 What is observed when a solution of potassium iodide solution is added to a solution of lead nitrate? Name the type of reaction. Write a balanced chemical equation to represent the above chemical reaction

Q28  What is meant by skeletal type chemical equation? What does it represent? Using the equation for electrolytic decomposition of water, differentiate between a skeletal chemical equation and a balanced chemical equation.

Q29 Why does the color of copper sulphate solution change when an iron nail is dipped in it? Write two observations.

Q30   Translate the following statement into chemical equation and then balance it Barium chloride reacts with aluminium sulphate to give aluminium chloride and a precipitate of barium sulphate. State the two types in which this reaction can be classified.